Mechanism for Controlling a Transmission Component

ABSTRACT

A transmission latching mechanism includes a component of a transmission gearset, a member secured to and able to rotate with the component, and a piston fixed against rotation and moveable alternately to latch the mechanism, thereby holding the member against rotation and to unlatch the mechanism, thereby releasing the member to rotate.

This application claims priority to and the benefit of U.S. ProvisionalApplication Nos. 61/446,147 and 61/446,149, filed Feb. 24, 2011, thefull disclosures of which are incorporated herein by reference.

This application is a continuation-in-part of pending U. S. applicationSer. No. 13/052,362, filed Mar. 21, 2011.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to an automatic transmission for a motor vehiclethat includes planetary gearsets and clutches and brakes whose state ofengagement and disengagement determines speed ratios produced by thetransmission.

2. Description of the Prior Art

In a front wheel drive vehicle, the axial space available for thetransmission is limited by the width of the engine compartment and thelength of the engine. In addition, the trend to increase the number ofratios available generally increases the number of components required.For these reasons, it is desirable to position components concentricallyin order to minimize axial length. The ability to position componentsconcentrically is limited, however, by the need to connect particularcomponents mutually and to the transmission case.

Furthermore, it is desirable for the output element to be located nearthe center of the vehicle, which corresponds to the input end of thegear box. An output element located toward the outside of the vehiclemay require additional support structure and add length on the transferaxis. With some kinematic arrangements, however, the need to connectcertain elements to the transmission case requires that the outputelement be so located.

One of the transmission control devices, such as the D brake, may beused only as a latching device rather than as a dynamic device. Tominimize parasitic viscous drag loss produced in the control device, itwould be better if the brake were a latching mechanism rather than ahydraulically-actuated friction brake having interleaved discs andspacer plates.

SUMMARY OF THE INVENTION

A transmission latching mechanism includes a component of a transmissiongearset, a member secured to and able to rotate with the component, anda piston fixed against rotation and moveable alternately to latch themechanism, thereby holding the member against rotation and to unlatchthe mechanism, thereby releasing the member to rotate.

The latching mechanism simplifies the brake, reduces the number ofcomponents as compared to the number required for ahydraulically-actuated friction brake, reduces the drag loss byeliminating the friction discs and plates, and requires a smaller spacethan the space required for a hydraulically-actuated friction brake.

The latching mechanism is a more robust component and requires lowercost to assemble and install than does a hydraulically-actuated frictionbrake.

The scope of applicability of the preferred embodiment will becomeapparent from the following detailed description, claims and drawings.It should be understood, that the description and specific examples,although indicating preferred embodiments of the invention, are given byway of illustration only. Various changes and modifications to thedescribed embodiments and examples will become apparent to those skilledin the art.

DESCRIPTION OF THE DRAWINGS

The invention will be more readily understood by reference to thefollowing description, taken with the accompanying drawings, in which:

FIG. 1 is a cross sectional side view of a multiple speed automatictransaxle;

FIG. 2 is cross sectional side view of the transaxle showing the frontand middle cylinder assemblies;

FIG. 3 is a side perspective view showing sleeves that are fitted on thefront support and middle cylinder assembly, respectively;

FIG. 4 is a view cross sectional side view of the transfer gears andshaft near the output of the transaxle of FIG. 1; and

FIG. 5 is a cross section side view taken through the latching mechanismand components of the transmission in the vicinity of the latchingmechanism.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring now to the drawings, FIG. 1 illustrates gearing, clutches,brakes, shafts, fluid passages, and other components of a multiple-speedautomatic transaxle 10 arranged substantially concentrically about anaxis 11.

A torque converter includes an impeller driven by an engine, a turbinehydrokinetically coupled to the impeller, and a stator between theimpeller and turbine. A transmission input shaft 20 is secured by aspline connection 21 to the turbine. The stator is secured by a splineconnection 22 to a front support 24, which is secured against rotationto a transmission case 26.

A double pinion, speed reduction planetary gearset 28 includes a sungear 30, secured by a spline connection 31 to input shaft 20; a carrier32, secured by a spline connection 33 to the front support 24; a ringgear 34, secured by a spline connection 35 to a front cylinder assembly36; a first set of planet pinions 38 supported on carrier 32 and meshingwith sun gear 30; and a second set of planet pinions 40, supported oncarrier 32 and meshing with ring gear 34 and the first pinions 38. Ringgear 34 rotates in the same direction as input shaft 20 but at a reducedspeed.

Rear gearset 46 and middle gearset 48 are simple planetary gearsets.Gearset 46 includes a set of planet pinion 50 supported for rotation oncarrier 52 and meshing with both sun gear 54 and ring gear 56. Gearset48 includes a set of planet pinions 58 supported for rotation on carrier60 and meshing with both sun gear 62 and ring gear 64. Sun gear 54 issplined to a shaft that is splined to a shell 66, on which shaft sungear 62 is formed, thereby securing the sun gears 54, 62 mutually and tothe shell 66. Carrier 52 is fixed to a shell 68. Carrier 60 and ringgear 56 are fixed to each other and to output pinion 70 through a shell72. Ring gear 64 is fixed to shell 74.

Front cylinder assembly 36, which is fixed to ring gear 34, actuatesclutches 76, 80. Plates for clutch 76 includes plates splined to frontcylinder assembly 36 alternating with plates splined to shell 74. Whenhydraulic pressure is applied to piston 78, the plates are forcedtogether and torque is transmitted between ring gears 34 and 64. Whenthe hydraulic pressure is released, ring gears 34 and 64 may rotate atdifferent speeds with low parasitic drag. Similarly, plates for clutch80 include plates splined to front cylinder assembly 36 alternating withplates splined to shell 66. When hydraulic pressure is applied to piston82, torque is transmitted between ring gear 34 and sun gears 54, 62.Pressurized fluid is routed from a control body 84, through frontsupport 24, into front cylinder assembly 36 between rotating seals.

Middle cylinder assembly 86, which includes carrier 32, actuates brake88. Plates for brake 88 include plates splined to carrier 32 alternatingwith plates splined to shell 66. When hydraulic pressure is applied topiston 90, the brake holds sun gears 54, 62 against rotation.Pressurized fluid is routed from the control body 84, through frontsupport 24, between planet pinions 38, 40, into middle cylinder assembly86. Due to the location of clutch pack 88, output element 70 is locatedin the more favorable position near the front of the gear box.

Rear cylinder assembly 92 is secured by a spline connection 93 fixed toinput shaft 20. When hydraulic pressure is applied to piston 94, theplates of clutch 96 transmit torque between input shaft 20 and carrier52. Similarly, when hydraulic pressure is applied to piston 98, theplates of clutch 100 transmit torque between input shaft 20 and sungears 54, 62. Pressurized fluid is routed from the control body 84, intorear cylinder assembly 92.

When hydraulic pressure is applied to piston 102, brake 104 holdscarrier 52 and shell 68 against rotation. A one-way brake 106 passivelyprevents carrier 52 and shell 68 from rotating in the negativedirection, but allows them to rotate in the forward direction. One-waybrake 106 may optionally be omitted and its function performed byactively controlling brake 104.

The D brake 104 is used only as a latching device not as a dynamicbrake. To minimize parasitic viscous drag loss produced in brake 104 itis desired that excess oil not be present in the brake. Therefore, anoil dam formed by an oil seal 103 between the piston 94 of E clutch 96and the inner race 107 of one-way brake 106 is provided to limit orprevent oil from entering the D brake 104. The inner radial end ofreturn spring 108 continually contacts the piston 102 that actuatesbrake 104. The outer radial end of return spring 108 continuallycontacts a fixed structure, so that the spring flexes as the piston 102moves in the cylinder of the D brake 104. In this way, return spring 108also participates in the oil dam by limiting or preventing radial flowof oil into the D brake 104 caused by centrifugal force.

This arrangement permits brake 88 and clutches 76, 80 to be mutuallyconcentric, located at an axial plane, and located radially outward fromthe planetary gearsets 28, 46, 48 such that they do not add to the axiallength of the gearbox. Similarly, clutches 96, 100 and brake 104 aremutually concentric and located radially outward from the planetarygearing 28, 46, 48. Clutches 76, 80, 96, 100 and brakes 88, 104, 106comprise the control elements.

As FIGS. 2A, 2B illustrate, the front cylinder assembly 36 is supportedfor rotation on the fixed front support 24 and carrier 34. The frontcylinder assembly 36 is formed with clutch actuation fluid passages,each passage communicating with one of the cylinders 114, 116 formed inthe front cylinder assembly 36. Cylinder 114 contains piston 78;cylinder 116 contains piston 82. One of the fluid passages in frontcylinder assembly 36 is represented in FIG. 2 by interconnected passagelengths 109, 110, 111, 112, through which cylinder 116 communicates witha source of clutch control hydraulic pressure. Another of the fluidpassages in front cylinder assembly 36, which is similar to passagelengths 109, 110, 111, 112 but spaced angularly about axis 11 frompassage lengths 109, 110, 111, 112, communicates a source of clutchcontrol hydraulic pressure to cylinder 114. Passage lengths 109 aremachined in the surface at the inside diameter of the front cylinderassembly 36.

The front cylinder assembly 36 is also formed with a balance volumesupply passage, similar to, but spaced angularly about axis 11 frompassage lengths 109, 110, 111, 112. The balance volume supply passagecommunicates with balance volumes 120, 122. As shown in FIG. 2A, thebalance volume supply passage includes an axial passage length 124,which communicates with a source of balance volume supply fluid andpressure, and a radial passage length 126, through which fluid flowsinto the balance volumes 120, 122 from passage 124. Passage 124 may be asingle drilled hole extending along a longitudinal axis and locatedbetween the two clutch balance areas of the A clutch and B clutch.Passage 124 carries fluid to cross drilled holes 126, which communicatewith the balance volumes 120, 122.

Coiled compression springs 128, 130, each located in a respectivebalance dam 120, 122, urge the respective piston 78, 82 to the positionshown in FIG. 2. Ring gear 34 is secured to front cylinder assembly 36by a spline connection 132.

Middle cylinder assembly 86 includes carrier 32, which is grounded onthe front support 24. Carrier 32 includes first and second plates 134,135 and pinion shafts secured to the plates, one pinion shaft supportingpinions 38, and the other pinion shaft supporting pinions 40. Plate 135is formed with a cylinder 140 containing a brake piston 90.

A source of brake actuating hydraulic pressure communicates withcylinder 140 through a series on interconnected passage lengths 142, 143and a horizontal passage length that extends axially from passage 143,through a web of carrier 32, between the sets of planet pinions 38, 40,to cylinder 140. These brake feed passages are formed in carrier 32.When actuating pressure is applied to cylinder 140, piston 90 forces theplates of brake 88 into mutual frictional contact, thereby holding sungears 54, 62 and shell 66 against rotation. A Belleville spring 146returns piston 90 to the position shown in FIG. 2, when actuatingpressure is vented from cylinder 140.

The front support 24 is formed with passages, preferably spaced mutuallyabout axis 11. These passages in front support 24 are represented in theFIGS. 1 and 2 by passage lengths 150, 151, 152, through which hydraulicfluid is supplied to clutch servo cylinders 114, 116, brake servocylinder 140, and balance dams 120, 122. A passage of each of the frontsupport passages communicates hydraulic fluid and pressure to cylinders114, 116 and balance dams 120, 122 of the front cylinder assembly 36through the fluid passages 109, 110, 111, 112, 113, 124 formed in thefront cylinder assembly 36. Another passage of each of the front supportpassages communicates hydraulic fluid and pressure to cylinder 140 ofthe middle cylinder assembly 86 through the fluid passages 142, 143 incarrier 32.

The front support 24 includes a bearing support shoulder 154, whichextends axially and over an axial extension 156 of the front cylinderassembly 36. A bushing 158 and bearing 160 provide for rotation of thefront cylinder assembly 36 relative to the front support 24. Thisarrangement of the front support 24, its bearing support shoulder 154,and front cylinder assembly 36, however, prevents radial access requiredto machine a passage or passages that would connect first passage 152 infront support 24 to the second passage 109 in the front cylinderassembly 36.

To overcome this problem and provide hydraulic continuity betweenpassage lengths 109, 152, first passage 152 is formed with an openingthat extends along a length of first passage 152, parallel to axis 11,and through an outer wall of the front support 24. The opening facesradially outward toward second passage 109. Similarly, second passage109 is formed with a second opening that extends along a length ofsecond passage 109, parallel to axis 11, and through an inner wall ofthe front cylinder assembly 36. The second opening faces radially inwardtoward first passage 152.

A first sleeve 162 is inserted axially with a press fit over a surfaceat an outer diameter of the front support 24, thereby covering theopening at the outer surface of passage length 152. Sleeve 162 is formedwith radial passages 164, 165, which extend through the thickness of thesleeve 162. Seals 176, located at each side of the passages 164, 165prevent leakage of fluid from the passages.

A second sleeve 170 is inserted axially with a press fit over the secondopening at the inside diameter of the front cylinder assembly 36,thereby covering and enclosing the length of the second opening in thesecond passage 109. Sleeve 170 is formed with radial openings, two ofwhich are represented in FIG. 2 by openings 172, 174, aligned with theradial passages 164, 165 formed in the first sleeve 162.

Sleeves 164 and 170 provides hydraulic continuity from the source offluid pressure carried in the passages of the front support 24 to thebalance dams 120, 122 and the servo cylinders 114, 116, 140, throughwhich clutches 76, 80 and brake 88 are actuated.

Sleeves 162, 170 also provide access that enables machining of the firstand second passages 152, 109 in the surface at the outside diameter offront support 24 and in the surface at the inside diameter of the frontcylinder assembly 36. FIG. 3 shows sleeves 162, 170 and three seals 176,which are fitted in recesses on sleeve 162 between each of its radialpassages 164, 165.

As FIG. 4 shows output pinion 70 meshes with a transfer gear 180, whichis formed integrally with transfer pinion 182 on a transfer wheel 184. Atransfer shaft 186, is secured at one end by a pinned connection 188 toa non-rotating housing component 190, and at the opposite end is seatedin a recess 192 formed in a non-rotating torque converter housingcomponent 194. Ball bearing 198 supports transfer wheel 184 on thetorque converter housing 194. Housing components 190, 194 comprise areaction component and may be formed integrally or preferably asseparate components.

Ball bearing 198 is supported radially by being seated on a surface 196of the torque converter housing 194. A shoulder 199 on torque converterhousing 194 contacts the right-hand axial surface of the inner race ofbearing 198, the second surface of bearing 198. A snap ring 200 contactsthe right-hand axial third surface 201 of the outer race of bearing 198.Shoulder 199 and snap ring 200 limit rightward axial movement of bearing198.

A shoulder 202 formed on gear wheel 184 contacts the left-hand axialfirst surface of the outer race of bearing 198. A thrust washer 204contacts a left-hand axial fourth surface 205 of the inner race ofbearing 198. The thrust washer 204 contacts a shoulder 206 formed ontransfer shaft 186. Shoulders 202 and 206 limit leftward axial movementof bearing 198

The ring gear 210 of a differential mechanism 212 meshes with transferpinion 182 and is supported for rotation by bearings 214, 216 on housing190, 194. Rotating power transmitted to output pinion 70 is transmittedthrough transfer gears 180, 182 and ring gear 210 to the input ofdifferential, which drives a set of vehicle wheels aligned with axis220.

A roller bearing 222 supports transfer wheel 184 on transfer shaft 186.The thickness of a washer 224, fitted in a recess 226 of housing 190, isselected to ensure contact between thrust washer 204 and the inner raceof bearing 198.

The output pinion 70 and transfer gears 180, 182 have helical gearteeth, which produce thrust force components in the axial directionparallel to axis 220 and in the radial direction, normal to the plane ofFIG. 5, which transmitting torque. A thrust force in the right-handdirection transmitted to the transfer gear wheel 184 is reacted by thetorque converter housing 194 due to its contact at shoulder 199 withbearing 198. A thrust force in the left-hand direction transmitted tothe transfer gear wheel 184 is reacted by the housing 190 due to contactbetween snap ring 200 and bearing 198, contact between bearing 198 andthrust washer 204, contact between the thrust washer and transfer shaft186, and contact between shaft 186, washer 224 and housing 190.

As shown in FIG. 1A, the D brake 104 includes a first set of thin discs230 secured to the outer race 232 of one-way brake 106 by a splineconnection, which permits the discs 230 to move axially and preventsthem from rotating relative to the race 232, which is fixed to thetransmission case or end cover against rotation.

Similarly, the D brake 104 includes a second set of thin discs 234secured to the inner race 107 of one-way brake 106 by a splineconnection, which permits the discs 234 to move axially and preventsthem from rotating relative to the inner race 107. The first and seconddiscs are interleaved, such that each of the first discs 230 has asecond disc 234 located on each axial side of the first disc.

Inner race 107 is fixed to the carrier 68 of gearset 46, such that discs234, inner race 107 and carrier 68 rotate together as a unit at the samespeed. The discs 230, 234 become frictional engaged mutually whenhydraulic pressure is applied to the cylinder 252 and piston 102 forcedthe discs into mutual contact, thereby fixing the inner race 107 andcarrier 68 against rotation. The discs 234 rotate freely relative todiscs 230 when hydraulic pressure is vented from cylinder 252.

Preferably the outer and inner races 232, 107 of one-way brake 106 areformed of a ferrous alloy of sintered powdered metal, and discs 230, 234are of steel. The reaction splines for the D brake 104 is preferably notformed in the aluminum case or aluminum end cover because of high localbearing stresses that would be induced in the case or end cover by thethin discs 230, 234. The discs 230, 234 are thin to reduce parasiticloss in the D brake 104. The D brake 104 reaction splines are formed asan integral part of the raceways 232, 107 of the one-way brake 106. Thebrake 106 is then splined to the transmission case.

Although the one-way transmission control member is described withreference to its being a brake 106, it may be a clutch, which connectsone member of a gearset to another member of the same gearset or adifferent gearset. Similarly, the hydraulically-actuated transmissioncontrol member is described with reference to its being a brake, but itmay be a clutch instead.

Preferably the one-way brake 106 is a rocker one-way brake of the typehaving a pivoting rockers, each rocker retained is a pocket and actuatedby centrifugal force and a compression spring, as described in U. S.Pat. Nos. 7,448,481 and 7,451,862.

FIG. 5 illustrates the D brake 104 as a latching mechanism 260, whichalternately connects carrier 52 and shell 68 to the transmission case,thereby holding the carrier against rotation, and disconnects carrier 52and shell 68 from the transmission case so that they can rotate freely.

Shell 68 is secured by a spline connection 261 to member 262. The innerrace 263 of a one-way brake 264 is secured by a spline connection 265 tomember 262. The outer race 266 of brake 264 is fixed against rotation bybeing secured to axially directed spline teeth 270 formed on the endcover 272 of the transmission case.

Latching mechanism 260 includes a piston 274, which moves substantiallyparallel to axis 11 and is fixed against rotation by being secured tothe axial spline teeth 270 formed on the end cover 272. Piston isactuated by actuating pressure in the cylinder 252 formed in the endcover 272 to slide rightward on spline teeth 270, thereby latchingmechanism 260. When actuating pressure in cylinder 252 is vented andrelease pressure is supplied through passage 271, 273 to a volume 282 ofcylinder 252, piston 274 is actuated by release pressure and the forceof a return spring 276 to slide leftward on spline teeth 270, therebyunlatching mechanism 260.

A dam 278, secured to the end cover 272 by a snap ring 280, supports adynamic seal 284, which, together with seal 286, hydraulically seals thevolume 282 located between the piston 274 and the dam 278.

Piston 274 is formed with a series of dog teeth 288, which are spacedmutually about axis 11 and located at the inner surface of the piston.Member 262 is similarly formed with a series of dog teeth 290, which arespaced mutually about axis 11 and located for engagement by teeth 288 aspiston 274 moves rightward in cylinder 252.

When cylinder 252 is pressurized and volume 282 is vented, piston 274moves rightward against the force of spring 276 causing teeth 288 toengage teeth 290, thereby connecting carrier 52 and shell 68 to the endcover 272 and holding the carrier and shell against rotation. Whencylinder 252 is vented and volume 282 is pressurized, piston 274 movesleftward causing teeth 288 to disengage teeth 290, thereby disconnectingcarrier 52 and shell 68 from the end cover 272 and allowing the carrierand shell to rotate freely.

The one-way brake 264 produces a torque reaction for carrier 52 andshell 68 in one rotary direction and allows the carrier and shell torotate freely in the opposite direction. Preferably the races 263, 266of one-way brake 264 are formed from a ferrous alloy of sinteredpowdered metal.

In accordance with the provisions of the patent statutes, the preferredembodiment has been described. However, it should be noted that thealternate embodiments can be practiced otherwise than as specificallyillustrated and described.

1. A transmission latching mechanism, comprising: a component of a transmission gearset; a member secured to and able to rotate with the component; and a piston fixed against rotation and moveable alternately to latch the mechanism, thereby holding the member against rotation and to unlatch the mechanism, thereby releasing the member to rotate.
 2. The mechanism of claim 1, further comprising: a casing secured against rotation, including a cylinder in which the piston moves in opposite axial directions, and spline teeth for securing the piston to the casing.
 3. The mechanism of claim 1, further comprising a one-way brake including: a first race fixed against rotation; a second race secured to the member, able to rotate in a first direction relative to the first race and prevented from rotating in a second direction relative to the first race.
 4. The mechanism of claim 3, further comprising: a casing secured against rotation, including a cylinder in which the piston moves in opposite axial directions, and spline teeth by which the piston and first race are secured to the casing.
 5. The mechanism of claim 1, wherein: the piston includes first dog teeth; and the member includes second dog teeth engageable with the first dog teeth as the piston moves in a first direction, and disengageable from the first dog teeth as the piston moves in a second direction opposite the first direction.
 6. The mechanism of claim 1, further comprising: a one-way brake including a first race fixed against rotation, and a second race able to rotate in a first direction relative to the first race and prevented from rotating in a second direction relative to the first race; wherein the member includes: second spline teeth for securing the component to the member; and third spline teeth for securing the second race to the member.
 7. The mechanism of claim 1, wherein the piston is hydraulically actuated to move in a first direction to latch the mechanism and hydraulically actuated to move in a second direction to unlatch the mechanism.
 8. A transmission latching mechanism, comprising: a component of a transmission gearset; a member secured to and able to rotate with the component; a piston fixed against rotation and moveable alternately to hold the member against rotation and to release the member for rotation; and a one-way brake including a first race fixed against rotation, and a second race secured to the member.
 9. The mechanism of claim 8, wherein the second race is able to rotate in a first direction relative to the first race and is prevented from rotating in a second direction relative to the first race.
 10. The mechanism of claim 8, further comprising: a casing secured against rotation, including a cylinder in which the piston moves in opposite axial directions, and spline teeth for securing the piston to the casing.
 11. The mechanism of claim 8, further comprising: a casing secured against rotation, including a cylinder in which the piston moves in opposite axial directions, and spline teeth by which the piston and first race are secured to the casing.
 12. The mechanism of claim 8, wherein: the piston includes first dog teeth; and the member includes second dog teeth engageable with the first dog teeth as the piston moves in a first direction, and disengageable from the first dog teeth as the piston moves in a second direction opposite the first direction.
 13. The mechanism of claim 8, wherein the member includes: second spline teeth for securing the component to the member; and third spline teeth for securing the second race to the member.
 14. The mechanism of claim 8, wherein the piston is hydraulically actuated to move in a first direction to latch the mechanism and hydraulically actuated to move in a second direction to unlatch the mechanism.
 15. A transmission latching mechanism, comprising: a component of a transmission gearset; a member secured to and able to rotate with the component; a casing secured against rotation, and including a cylinder; and a piston fixed to the casing against rotation, and moveable in the cylinder in opposite axial directions alternately to hold the component against rotation and to release the member for rotation.
 16. The mechanism of claim 1, further comprising a one-way brake including: a first race fixed against rotation; a second race secured to the member, able to rotate in a first direction relative to the first race and prevented from rotating in a second direction relative to the first race.
 17. The mechanism of claim 16, wherein the casing includes spline teeth by which the piston and first race are secured to the casing and fixed against rotation.
 18. The mechanism of claim 15, wherein: the piston includes first dog teeth; and the member includes second dog teeth engageable with the first dog teeth as the piston moves in a first direction, and disengageable from the first dog teeth as the piston moves in a second direction opposite the first direction.
 19. The mechanism of claim 15, further comprising: a one-way brake including a first race fixed against rotation, and a second race able to rotate in a first direction relative to the first race and prevented from rotating in a second direction relative to the first race; and wherein the member includes second spline teeth for securing the component to the member, and third spline teeth for securing the second race to the member.
 20. The mechanism of claim 1, wherein the piston is hydraulically actuated to move in a first direction to latch the mechanism and hydraulically actuated to move in a second direction to unlatch the mechanism. 